1. Field of the Invention
The present invention relates generally to a flat cathode ray tube, and is directed more particularly to a flat cathode ray tube compact in size.
2. Description of the Prior Art
In an ordinary cathode ray tube such as a television receiver tube an electron gun is so arranged that it faces the phosphor screen of the tube and extends along a direction substantially perpendicular to the phosphor screen to the rear side. Therefore, the depth of the evacuated envelope of the cathode ray tube becomes relatively large.
On the contrary, a so-called flat cathode ray tube is proposed in which the electron gun is located to be extended in the horizontal or vertical direction along the surface of the phosphor screen of the cathode ray tube to make its envelope flat.
In such a prior art flat cathode ray tube, in order to scan the phosphor screen of the tube by the electron beam emitted from its electron gun, electromagnetic deflection means or devices are generally used to deflect the electron beam in both the horizontal and vertical directions. However, the horizontal and vertical electromagnetic deflection devices are complicated in construction and large in thickness, so that the prior art flat cathode ray tube can not sufficiently exhibit its inherent advantage.
Recently, such a flat cathode ray tube has been proposed in which both the horizontal and vertical deflection of the electron beam are carried out electrostatically. In this case, the deflection devices thereof become compact, but deflection distortion is apt to be generated on the deflection in the direction, in which a large deflection angle is required, namely the deflection in the direction substantially perpendicular to the axial direction of the electron gun opposing the phosphor screen. In this case, a large deflection voltage is required and hence large power is necessary for its circuitry.